1. Field of the Invention
The present invention relates to a method of controlling the charging of a lithium ion battery, nickel-cadmium (Ni--Cd) battery, nickel-metal hydride (Ni--MH) battery or similar rechargeable battery, and a charger for practicing the same.
2. Description of the Background Art
Modern electronic apparatuses including notebook type personal computers and digital cameras are extremely small in size and light in weight and are often powered by rechargeable batteries. Rechargeable batteries for such an application include a lithium ion battery, an Ni--Cd battery and an Ni--MH battery. A lithium ion battery, for example, is a nonaqueous rechargeable battery using an organic solvent of lithium salt as an electrolyte. This kind of battery generates an electromotive force based on oxidation reduction derived from the migration of lithium ions. In this respect, a lithium ion battery is distinguishable from the other rechargeable batteries using water-soluble electrolytes and generating electricity based on electrochemical reactions in which water join. The nonaqueous rechargeable battery is advantageous over the other rechargeable batteries in that it implements a high voltage between battery terminals for a single battery or cell, a high capacity, and a high output. Charging methods for enhancing the performance of the nonaqueous rechargeable battery itself and further promoting the effective use of such a battery are under investigation.
It has been customary with a charger for charging a rechargeable battery to, e.g., insert a charge current sensing circuit in a charge line for charging the battery. The charge current sensing circuit senses a charge current flowing through the charge line. When the charge current decreases below a preselected value, the charger determines that the battery connected thereto has been fully charged. The charge current sensing circuit, however, increases a part mounting area required of the charger and thereby obstructs the miniaturization of the charger. Moreover, the conventional charge current sensing circuit needs a highly accurate and therefore expensive configuration, making the arrangement of the charger complex and sophisticated.